feat(joinir): Phase 254-255 - Pattern 6 (ScanWithInit) + exit PHI DCE fix

## Phase 254: Pattern 6 (ScanWithInit) Detection & JoinIR Lowering

Pattern 6 detects index_of/find/contains-style loops:
- Loop condition: i < x.length()
- Loop body: if with method call condition + early return
- Step: i = i + 1
- Post-loop: return not-found value (-1)

Key features:
- Minimal lowering: main/loop_step/k_exit functions
- substring hoisted to init-time BoxCall
- Two k_exit jumps (found: i, not found: -1)
- Tests: phase254_p0_index_of_min.hako

## Phase 255 P0: Multi-param Loop CarrierInfo

Implemented CarrierInfo architecture for Pattern 6's 3-variable loop (s, ch, i):
- i: LoopState (header PHI + exit PHI)
- s, ch: ConditionOnly (header PHI only)
- Alphabetical ordering for determinism
- All 3 PHI nodes created correctly
- Eliminates "undefined ValueId" errors

## Phase 255 P1: Exit PHI DCE Fix

Prevents exit PHI from being deleted by DCE:
- PostLoopEarlyReturnStepBox emits post-loop guard
- if (i != -1) { return i } forces exit PHI usage
- Proven pattern from Pattern 2 (balanced_depth_scan)
- VM/LLVM backends working

## Test Results

✅ pattern254_p0_index_of_vm.sh: PASS (exit code 1)
✅ pattern254_p0_index_of_llvm_exe.sh: PASS (mock)
✅ Quick profile: json_lint_vm PASS (progresses past index_of)
✅ Pattern 1-5: No regressions

## Files Added

- src/mir/builder/control_flow/joinir/patterns/pattern6_scan_with_init.rs
- src/mir/join_ir/lowering/scan_with_init_minimal.rs
- apps/tests/phase254_p0_index_of_min.hako
- docs/development/current/main/phases/phase-254/README.md
- docs/development/current/main/phases/phase-255/README.md

🧠 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

docs/development/current/main/phases/phase-146/README.md

@@ -1,6 +1,6 @@
 # Phase 146: Loop/If Condition ANF Implementation
 
-**Status**: P0 in progress / P1 planned
+**Status**: P0/P1/P147 complete
 **Date**: 2025-12-19
 **Context**: Phase 145 P0/P1/P2 complete (ANF infrastructure). Phase 146/147 adds condition expression support.
 
@@ -15,7 +15,7 @@ Phase 146 enables ANF (A-Normal Form) transformation for loop and if conditions,
 ### Implementation
 
 1. **expr_lowerer_box.rs**: Added scope check to ANF routing (L54-79)
-   - `PureOnly` scope: Skip ANF (P1 will enable)
+   - `PureOnly` scope: Skip ANF (P1 で dev-only 有効化)
    - `WithImpure` scope: Try ANF (Phase 145 behavior)
 
 2. **post_if_post_k.rs**: Replaced legacy inline lowering with SSOT (L271-285)
@@ -43,30 +43,48 @@ Phase 146 enables ANF (A-Normal Form) transformation for loop and if conditions,
 - [x] Scope check added to ANF routing
 - [x] Legacy inline lowering removed from post_if_post_k.rs
 - [x] SSOT unified (lower_expr_with_scope is only entry point)
-- [ ] Build passes (cargo build --release)
-- [ ] Tests pass (cargo test --release --lib)
-- [ ] Phase 145 regression: 0 failures
-- [ ] Fixture exit code: 7 (VM + LLVM EXE)
+- [x] Build passes (cargo build --release)
+- [x] Tests pass (cargo test --release --lib)
+- [x] Phase 145 regression: 0 failures
+- [x] Fixture exit code: 7 (VM + LLVM EXE)
 
-## Phase 146 P1: 条件式 ANF 有効化（planned）
+## Phase 146 P1: 条件式 ANF 有効化（done）
 
 **Goal**: Enable ANF in conditions for `PureOnly` scope behind a dev flag, starting with whitelisted intrinsic (`String.length()`).
 
-### Planned Implementation
+### Implementation
 
-1. **expr_lowerer_box.rs**: Allow ANF for PureOnly with env flag
-2. **anf/execute_box.rs**: Add Compare operator support
+1. **expr_lowerer_box.rs**: Allow ANF for PureOnly with `HAKO_ANF_ALLOW_PURE=1`
+2. **anf/execute_box.rs**: Add Compare operator support (`== != < <= > >=`)
 3. **config/env/joinir_dev.rs**: Add `anf_allow_pure_enabled()` function
+4. **Whitelist**: KnownIntrinsic registry を利用し、`String.length()` のみ許可
 
-## Phase 147 P0: 複合条件の順序固定（planned）
+### Files Created (P1)
+
+- `apps/tests/phase146_p1_if_cond_intrinsic_min.hako` (exit code 7)
+- `tools/smokes/.../phase146_p1_if_cond_intrinsic_vm.sh`
+- `tools/smokes/.../phase146_p1_if_cond_intrinsic_llvm_exe.sh`
+
+### Acceptance Criteria (P1)
+
+- [x] `HAKO_ANF_ALLOW_PURE=1` で PureOnly scope の ANF が有効化される
+- [x] `String.length()` のみ許可され、他の MethodCall は out-of-scope
+- [x] Fixture exit code: 7 (VM + LLVM EXE)
+
+## Phase 147 P0: 複合条件の順序固定（done）
 
 **Goal**: Extend recursive ANF to Compare operators for compound conditions.
 
-**Status**: Not yet implemented
+### Implementation
 
-### Planned Implementation
+1. **anf/contract.rs**: `AnfParentKind::Compare` を追加
+2. **anf/plan_box.rs**: Compare vs BinaryOp を判別して ParentKind を決定
+3. **anf/execute_box.rs**: Compare でも再帰的 ANF を適用（left-to-right）
 
-1. **anf/plan_box.rs**: Add Compare case to plan_expr()
+### Acceptance Criteria (P147)
+
+- [x] Compare を含む複合条件でも評価順序が固定される
+- [x] ANF の再帰が Compare にも適用される
 
 ## Testing
 
@@ -82,6 +100,20 @@ Phase 146 enables ANF (A-Normal Form) transformation for loop and if conditions,
 # Expected: exit 7
 ```
 
+### P1 Smoke Tests
+
+```bash
+# VM (dev-only)
+HAKO_ANF_DEV=1 HAKO_ANF_ALLOW_PURE=1 \
+  ./tools/smokes/v2/profiles/integration/apps/phase146_p1_if_cond_intrinsic_vm.sh
+# Expected: exit 7
+
+# LLVM EXE (dev-only)
+HAKO_ANF_DEV=1 HAKO_ANF_ALLOW_PURE=1 \
+  ./tools/smokes/v2/profiles/integration/apps/phase146_p1_if_cond_intrinsic_llvm_exe.sh
+# Expected: exit 7
+```
+
 ### Regression Tests
 
 Phase 145 smokes must still pass: